This invention relates in general to radiation imaging systems providing both two-dimensional target data as well as target depth or ranging information.
Target imaging systems for obtaining depth or ranging data as presently known, involve the emission of electromagnetic radiation directed toward the target object so as to measure the time it takes for return of target reflected echo pulses. The extraction of target range data from echo pulse signals reflected from a target illuminated by light pulses emitted by a transmitter, is disclosed for example in each of U.S. Pat. Nos. 4,687,326, 4,722,599 and 4,920,412 to Corby, Jr., Frueget et al. and Gerdt et al., respectively. According to the Corby Jr., patent, three dimensional imaging of the target is essentially achieved by parallax involving comparison of target reflected radiation luminescence in different directions. The measurement of target depth from backscattered light intensities without any two-dimensional imaging, is disclosed in the Frueget et al. patent. The disclosure in the Gerdt et al. patent is of most interest because it teaches the provision of target depth measurements by use of a short laser pulse and a gated receiver. Three dimensional imaging according to the Gerdt et al patent would, however, require emission of a series of pulses from a laser source to obtain a corresponding series of range-gated echo pulses picked up at various distances from the laser source.
It is therefore an important object of the present invention to provide a target imaging system wherein echo pulses reflected from the target provide more accurate three dimensional imaging data extracted by means of a range gated receiver at a single receiving location.
An additional object in accordance with the foregoing object is to provide an echo pulse receiving system in which each pulse of short duration is an independent source of both two-dimensional imaging and ranging data at the receiving location so as to avoid image blurring because of target movement.